Field of Invention
The present invention relates to a coil and, in particular, to a coil with high space factor.
Related Art
Inductance devices applied to electromagnets and transformers are mostly composed of coil, which is made by winding an enamel wire.
It is desired to provide a coil with low cost and high space factor (or space coefficient). The space factor is the ratio of the volume occupied by the wire in the winding to the total volume of the winding. The coil with higher space factor usually has smaller magnetic loss. Moreover, since the coil is the major component of a motor, the motor can be manufactured with smaller size, lighter weight and more powerful as the coil's space factor is increased. Besides, when applying to the high-frequency application, the skin effect of the coil current may cause some energy loss. The skin effect is the tendency of an alternating electric current (AC) to become distributed within a conductor such that the current density is largest near the surface of the conductor, and decreases with greater depths in the conductor. In this case, since the flat wire has larger surface area than the circular wire, using the flat wire to manufacture the high-frequency coil can effectively decrease the energy loss. Moreover, the flat wire also has a better heat-dissipation capability.
However, since the conventional coil is made by winding the enamel wire, it is hard to increase the space factor thereof. To fabricate a motor with small size and light weight, the performance of the motor will be decreased due to the low space factor of the coil. If the coil is made of a flat wire, it needs a special manufacturing process to form the coil as the flat surface of the flat wire is perpendicular to the central axis of the coil. Accordingly, the manufacturing cost of the coil by the flat wire is higher.
Therefore, it is an important subject of the present invention to provide a coil with low cost, high space factor and low energy loss, and moreover, to provide a coil made of a flat wire.